(1) Field of the Invention
The present invention relates to enhancement in milk production, and more particularly to such improvement by application of dihydroquinoline compounds to the feed of lactating animals.
(2) Description of the Prior Art
The dairy industry is always searching for techniques for increasing the production of milk from dairy cows. In particular, the industry is always searching for ways to increase milk production on a per cow basis—that is, volume of milk produced per cow—as well as ways to increase milk production on a feed efficiency basis—that is, volume of milk per pound of feed.
Ethoxyquin (6-ethoxy-1,2-dihydro-2,2,4-trimethylquinoline) has been applied to the feed of cattle, but for reasons other than for increasing milk production. For example, U.S. Pat. No. 6,017,564 describes a method for improving health, feed efficiency (that is, weight gain per pound of feed consumed) or weight gain of cattle that have been stressed, such as by their shipping or deprivation of food and/or water, by adding ethoxyquin to their feed. In particular, that patent discusses the treatment of receiving cattle upon their arrival at the feed yard and focuses on beef cattle wherein the primary goal is health and weight gain of the cattle prior to slaughter. U.S. Pat. No. 5,891,491 also discloses a method that involves incorporating ethoxyquin in cattle feed. There, the ethoxyquin is used to extend the shelf life of beef derived from the cattle.
Ethoxyquin also has been reported to have been used in a concentration of 0.05 to 0.1% (500-1,000 ppm) in a feed composition for breeding cattle with N3 fatty acid-accumulated beef. See Canadian Patent No. 2,087,792. According to page 10 of that Canadian patent, the ethoxyquin is used as an anti-oxidant and “also plays an anti-oxidation activity in the cattle's body, as well as in the feed composition, to prevent the oxidative decomposition of N3 fatty acid in spoilage of feed during long-term storage.” And, in U.K., Patent No. 144,024, the possible candidacy of ethoxyquin as an anti-oxidant component of a food or feed supplement to prevent the occurrence of or to retard cancer is reported. It is suggested there that the ethoxyquin concentration should be sufficient for the daily consumption to be about 0.01 to 500 mg.
Ethoxyquin has been reported to have been added at a rate of from about 125 ppm by weight to about 150 ppm by weight on a dry matter intake (“DMI”) basis to the diets of dairy cattle to reduce the oxidized flavor of milk, but the dietary ethoxyquin in those trials has been reported to result in the appearance of ethoxyquin in the fat of the resulting milk, while the tolerance of ethoxyquin in milk is zero. Dunkley et al., Supplementing Rations with Tocopherol and Ethoxyquin to Increase Oxidative Stability of Milk, J. Dairy Sci., Vol. 50, No. 4, pp. 492-499 (1967) (“Dunkley I”); Dunkley et al., Compounds in Milk Accompanying Feeding of Ethoxyquin, J. Dairy Sci., Vol. 51, No. 8, pp. 1215-1218 (1968).
Dietary ethoxyquin also has been applied to animals other than cattle. For example, it has been reported to reduce or to prevent certain maladies associated with a deficiency of Vitamin E, in particular, encephalomalacia, exudative diathesis in chicks, muscular dystrophy in chicks and lambs and fetal resorption in rats. It is unclear whether these effects have been direct effects on the target tissues or indirect effects through preventing lipid oxidation and reducing Vitamin E usage or by preventing Vitamin E destruction in the diet or the gut. Miller and White, Nutr. Rep. Int. 12:245-252 (1975); Whanger et al., Nutr. Rep. Inst. 13:159-173 (1976). However, dietary ethoxyquin has been reported to prevent lipid oxidation in muscle tissues in broilers and layers. Bartov and Bornstein, Br. Poultry Sci. 18:59-68 (1977); Combs and Regenstein, Poultry Sci. 59:347-351 (1980). The ethoxyquin concentration in the feed in the broiler study was 75 to 150 ppm by weight, and 150 ppm of ethoxyquin was found to be as effective as about 15 ppm alpha-tocopherol acetate. In the layer study, the ethoxyquin concentration was 500 ppm. Ethoxyquin was detected in the muscle tissue of poultry and lambs, suggesting that the effect is directly in the tissue, demille et al., Can. J. Anim. Sci. 52:351-361 (1972).
Despite these reports of uses of ethoxyquin in feed, there has been no recognition in the industry of which applicants are aware that ethoxyquin may have any effect on the efficiency of milk production. In any event, however, the dairy industry is still searching not only for ways to improve milk production of dairy cattle, but also for ways to improve feed efficiency in milk production.